dt-bindings: clock: Add clock ids of ref clocks in GCC for SHIMA

Add clock ids for gcc_gpu_iref_clk and gcc_ufs_1_clkref_en in GCC
for SHIMA.

Change-Id: Ib1b053e14a1063704789e12b0ea97c74a0634a78
Signed-off-by: Jagadeesh Kona <jkona@codeaurora.org>